The invention relates generally to cryogenic liquid dispensing stations and, more specifically, to portable self-contained dispensing stations for liquid natural gas.
Interest in the use of liquid natural gas (LNG) as a fuel for motor vehicles has increased dramatically in recent years. Entire fleets of government and industrial vehicles have successfully been converted to natural gas. Some privately-owned vehicles have been converted as well. Congress has passed an energy bill that requires increased use of alternative fuels in government and private fleets. Several factors have influenced this increasing use of LNG as a fuel in motor vehicles. LNG is relatively inexpensive. In addition, it burns very cleanly, making it much easier for fleets to meet more restrictive pollution emission standards.
LNG is stored and dispensed as a liquid because such an arrangement reduces the space necessary to contain the fuel in the dispensing station and the vehicle. An LNG fueling facility typically includes a large LNG storage tank and a dispensing system. Given that LNG is a cryogenic fluid, and thus has a boiling point below xe2x88x92150xc2x0 F., the tank must be well insulated. In addition, the dispensing system must be capable of delivering LNG in a homogenous liquid phase so that accurate metering occurs and the maximum amount of fuel is stored in the vehicle""s tank.
Pilot programs for testing and demonstration of the viability of LNG as an alternative fuel require pilot dispensing stations. Because of the unique storage requirements for LNG, it is impractical and economically unfeasible to modify existing gasoline facilities for LNG. It is therefore advantageous to minimize the capital investment in site improvements required to install LNG pilot dispensing stations since it is difficult to recapture such outlays during the relatively short life of the facility. An ideal LNG dispensing station thus will be one that is portable and self-contained to permit quick transport and installation at different distribution sites. Such a station would also permit fluid delivery and accurate metering to be initiated almost instantly.
In addition, National Fire Protection Association (NFPA) guidelines (NFPA 59A, Para 108) for spill containment require impounding areas that hold the entire LNG capacity of the station in the event of a catastrophic spill. Furthermore, in accordance with NFPA guidelines, electrical controls must either be designed for explosion-proof conditions or be situated in a safe area that is outside of the Division 1 and Division 2 areas illustrated in FIG. 1 at 8 and 9, respectively. Explosion-proof controls are costly. As a result, the latter option is preferable.
In response to the above demands, the filling station of commonly owned U.S. Pat. No. 5,682,750 to Preston et al. was developed. Such a station, which is marketed under the name QRS by Chart Inc. of Burnsville, Minn., provides a moveable skid constructed of a welded I-beam framework that is configured in a rectangular box shape. The side walls of the framework are formed of vertically positioned I-beams, cross members and metal fencing. Metal panels are fastened around the bottoms of the side walls to form what is essentially a stainless steel xe2x80x9cbathtub.xe2x80x9dMounted upon the framework is a bulk storage tank and an instant-on delivery system wherein the system pump and meter are mounted within a sump. The sump is flooded with LNG so that the pump and meter are maintained at the proper temperature for instant-on operation.
While the system of the Preston et al. ""750 patent performs very well and is very effective, its manufacturing cost is quite high. A demand thus exists for a lower-cost portable self-contained LNG dispensing station. A demand also exists for a portable self-contained LNG dispensing station that fits within a standard sized container so that it may be shipped on equipment available throughout the world.
Accordingly, it is an object of the present invention to provide a portable self-contained LNG dispensing station that permits quick transport and installation at different distribution sites.
It is another object of the present invention to provide a portable self-contained LNG dispensing station that permits dispensing to be initiated almost instantly.
It is another object of the present invention to provide a portable self-contained LNG dispensing station that meets safety guidelines for spill containment and electrical controls positioning.
It is another object of the present invention to provide a portable self-contained LNG dispensing station that does not require explosion-proof electrical controls and equipment.
It is still another object of the present invention to provide a portable self-contained LNG dispensing station that is economical to manufacture.
It is still another object of the present invention to provide a portable self-contained LNG dispensing station that may be shipped on equipment available throughout the world.
The present invention is directed to a portable self-contained dispensing station for dispensing LNG to motor vehicles. The station features a container, preferably an ISO container, having a pair of opposing side walls, a pair of opposing end walls and a bottom panel. The bottom panel, opposing side walls and opposing end walls of the container are lined with stainless steel sheets so that cryogenic liquid does not leak out of the container. The lined container defines a spill containment volume that is sized to hold all of the supply of LNG in the bulk tank of the dispensing station. The container is divided into a ventilated portion and a covered portion with the covered portion including a roof positioned thereon in opposition to the bottom panel and the ventilated portion including an open top.
A bulk tank is positioned within the container and contains a supply of cryogenic liquid with a head space thereabove. A vent valve is in communication with the head space of the bulk tank and positioned beneath the open top of the ventilated portion of the container. A pump is positioned within the container and in communication with the bulk tank so that when the pump is activated, LNG is dispensed from the dispensing station. A sump that is in communication with the bulk tank receives LNG and the pump is submerged in the LNG so as to avoid two-phased flow therethrough.
An electric control panel for operating the pump, microprocessor and the automated valves of the dispensing station is positioned on a lower portion of the end panel of the covered portion of the container so as to be in an area permitted by NFPA guidelines.
The following detailed description of embodiments of the invention, taken in conjunction with the appended claims and accompanying drawings, provide a more complete understanding of the nature and scope of the invention.